This invention relates to delay circuits.
A typical delay circuit delivers an output pulse at some predetermined delay time after receiving an input pulse. The predetermined delay period (between the input and output pulses) must be accurate and repeatable.
When a delay circuit is needed to provide a fixed specific delay period for logic located on an integrated circuit, a precision discrete delay circuit is typically provided in a separate package. Alternatively an RC-type delay circuit provided directly on a hybrid substrate may be adjusted at the time of manufacture (by laser trimming of resistors) to compensate for manufacturing variations in the delay characteristics of integrated circuit elements. Thus the delay period may nominally be set to the desired fixed delay. Typical delay lines do not permit variations of the delay amount to accommodate additional small changes in the delay characteristics that may occur during operation due to temperature and supply voltage changes.
Discrete delay circuits in which the delay period is selectable typically use tunable LC circuits or tapped delay lines feeding multiplexers.